The present invention relates to a printing device, in particular a franking machine, having a print head that can be moved along a first direction into a first longitudinal position and a station, provided to cooperate with the print head located in the first longitudinal position, for cleaning and/or maintaining and/or retaining and storing the print head.
Particularly in the context of printers that operate on the ink jet principle, it is generally necessary to maintain the print head regularly, that is to say among other things to xe2x80x9cfirexe2x80x9d the nozzles in accordance with a specific pattern without any medium to be printed and to wipe off the row or rows of nozzles with a wiper in order to remove contaminants.
Furthermore, it is necessary to cover the nozzles of the print head when they are not used for a relatively long time, by means of a cap or the like which makes appropriately tight contact in order to prevent the ink from drying out and therefore the nozzles from becoming blocked. In order to achieve the covering seal, the cap generally has a relatively soft peripheral edge, which defines a plane parallel to the first direction, that is to say the direction of travel of the print head, and can be placed sealingly around a ledge on the print head. For the purpose of covering, the print head is moved from the outside against this edge of the cap, the edge being deformed because of its elasticity and giving way to the print head. Once the print head has then reached its end position with respect to the cap, the edge can return into its original shape and is placed around the ledge on the print head.
However, that prior art device has the disadvantage that the cap is firstly subjected to relatively high wear because of the frequent deformation. In addition, it is relatively complicated to produce, since some tolerances have to be complied with in order in fact to achieve a good sealing behavior from the cap.
In other devices of the generic type, such as the one disclosed, for example, in U.S. Pat. No. 5,627,573 (European patent application EP 0 720 912 A2), it is proposed to lift the cap against the print head by an appropriate mechanism to be operated as the print head moves, in order in this way to achieve the sealing. In that case, although comparatively good sealing is achieved with low wear of the cap, the print head has to be moved relatively far in the first direction in order to produce the appropriate stroke for the cap. In addition, because of the operating mechanism for the cap, which has to be integrated, the station is relatively large and complicated. Both aspects lead to a configuration that is generally undesirably large.
It is accordingly an object of the invention to provide a printing apparatus, which overcomes or at least limits the above-mentioned disadvantages of the heretofore-known devices and methods of this general type to a minimum and which ensure simple, cost-effective production with a low overall size.
With the foregoing and other objects in view there is provided, in accordance with the invention, a printing device, in particular a franking machine, comprising:
a print head movably disposed along a first direction into a first longitudinal position;
a station disposed to cooperate with the print head located in the first longitudinal position for one of cleaning, maintaining, and retaining the print head; and
the print head being movable toward the station in a second direction transverse to the first direction, for cooperating with the station.
That is, the print head is either configured to be movable in the second direction, and/or movably mounted in the second direction.
The present invention is based on the technical teaching that a configuration which is simple and cost-effective to produce and takes up little overall space may be achieved if the print head, in order to cooperate with the station, is configured and/or arranged to move toward the station in a second direction running transversely with respect to the first direction.
It has been shown that, by using such a configuration, ultimately smaller configurations may be achieved. Because of the overall space occupied by it as compared with the station or its individual components, the print head provides more possible ways for an ultimately simpler and smaller configuration of a mechanism via which the print head and station can be moved toward each other. The necessary guides and drive means or drive devices can be configured to be correspondingly larger and simpler, without the overall space required for this being increased significantly. In particular, because of the comparatively large extent of the print head, more free space is available for the distribution of the individual functional elements, which results in a considerably simpler, more robust configuration.
The travel movement of the print head along the second direction can be achieved in any desired way. For example, the print head can complete a simple linear movement along the second direction, in order to be moved toward the station. This can be carried out after the print head has already reached its first longitudinal position. The movement along the second direction can, however, also start while the print head is still being moved along the first direction, so that the print head ultimately approaches the station on a planar curved path.
In particularly simple variants of the device according to the invention, provision is made for the print head to be designed or arranged such that it can be pivoted about a pivot axis running substantially parallel to the first direction. The pivoting mounting may be achieved in a particularly simple and small manner. The pivoting mounting is preferably simply formed by the appropriately configured longitudinal guide of the print head along the first direction, which also results in an additional space saving.
In order to effect the movement along the second direction, a separate drive can be provided. However, the movement along the second direction is preferably achieved by moving the print head along the first direction, in order in this way to save an additional drive.
In this case, a guide device designed to cooperate with the print head is preferably provided in order to guide the print head during the movement in the second direction when the print head is moving along the first direction. By this means, in a simple way, a defined movement of the print head in the direction of the station can be achieved. In this case, the accelerations acting on the print head during the movement can additionally also be adjusted by means of appropriate configuration of the guide device.
The guide device can be formed by one or more separate components. It is preferably formed as part of a longitudinal guide provided to guide the print head along the first direction, so that a further space saving is achieved.
As mentioned above, the movement along the second direction is preferably achieved by moving the print head along the first direction. In advantageous variants, provision is made, to this end, for the guide device to be designed to effect the movement of the print head along the second direction. In other words, the guide device acts on the print head in such a way that the latter is moved along the second direction.
In this case, a first guide face on the guide device generally cooperates with a second guide face on the print head. In order to ensure defined guidance of the print head, it is preferably ensured that the first and second guide faces make contact with each other during the entire movement. This can be done by the guide being designed in the manner of a positive guide. Likewise, however, it is possible to ensure, by suitable means, for example by springs but also by the force of gravity, that a contact force always acts between the two guide faces.
In particularly simply configured variants of the device according to the invention, the print head is designed or arranged to move toward the station in the second direction on account of its weight. In this case, as already mentioned, it can preferably be guided by a guide device in order to ensure a defined movement in the direction of the station.
The station can be configured and designed in any desired known way. The station preferably comprises a cap for covering the printing elements of the print head. In order to achieve an efficient sealing force acting during the cooperation with the print head, the cap is preferably mounted in a sprung manner in the station, at least along the second direction. In this case, the sprung mounting not only ensures the sealing force but also permits the compensation of positioning inaccuracies between the print head and the cap. Particularly good compensation for such inaccuracies results when the mounting of the cap is additionally designed in such a way that it can be moved transversely with respect to the second direction within specific limits.
In further preferred variants, the station comprises a wiping device for wiping the outlet region of the printing elements of the print head and, in addition or alternatively, further functional elements of conventional stations for cleaning, maintaining or preserving the print head.
In the sense of the present invention, the term print head is to be understood to mean not just that part of a printing device which contains the printing elements, for example the nozzles. Instead, the term is also to comprise structural units from the printing elements and associated storage containers for the printing medium, and also possible mountings into which such structural units are inserted. Otherwise, it goes without saying in this case that the invention may be applied to print heads operating in accordance with any desired printing principles.
Furthermore, the movement of the print head toward the station is not intended to be interpreted to the effect that the entire print head is moved toward the station as a self-contained unit. Instead, it may be sufficient if the part of the print head that carries the printing elements and which is ultimately certainly intended to cooperate with the maintenance station is moved toward the station.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a printing device, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.